This invention relates to batteries.
Batteries, such as primary alkaline batteries, are commonly used as energy sources. Generally, alkaline batteries include a cathode, an anode, a separator, and an electrolytic solution. The cathode can include an active material, such as manganese dioxide or nickel oxide, carbon particles that enhance the conductivity of the cathode, and a binder. The anode may be, for example, a gel including zinc particles as the active material. The separator is disposed between the cathode and the anode. The electrolytic solution can be, for example, a hydroxide solution that is dispersed throughout the battery.
Desirable primary alkaline batteries have a zinc anode that generates little hydrogen. Typically, primary batteries use amalgamated zinc anodes. Mercury added to the zinc helps decrease the amount of hydrogen generated from, for example, water in contact with the zinc. Hydrogen generation in the anode can cause pressure to build up in the battery which can lead to leaks.
The invention features a primary alkaline battery including a zinc anode free of lead, mercury, or cadmium. The cathode is a hydrogen-absorbing cathode material. The hydrogen-absorbing cathode material presently absorbs hydrogen at a faster rate than electrochemically-produced manganese dioxide. For example, the hydrogen-absorbing cathode material absorbs at least 20% more hydrogen than an equivalent amount of electrochemically-produced manganese dioxide within an equivalent time interval.
By eliminating added lead, mercury, or cadmium from the anode, a safer, more environmentally friendly battery can be produced. The zinc free of lead, mercury, or cadmium is free of added lead, mercury, or cadmium. The zinc contains less than 100 ppm, preferable less than 25 ppm, and more preferably less than 5 ppm of lead, mercury or cadmium. Elimination of a substantial weight and volume of mercury in particular allows a higher gravimetric and volumetric energy density to be achieved. Primary batteries containing electrochemically-produced manganese dioxide (EMD) cathodes and zinc anodes free of lead, mercury, or cadmium suffer from increased zinc gassing compared to batteries that contain mercury, lead or cadmium in the anode. The increased gassing cans cause the battery to leak or rupture. By replacing the EMD cathode with another cathode material having higher hydrogen absorption rate than EMD, the cathode can absorb the hydrogen and reduce the incidence of leakage and rupture. The hydrogen-absorbing cathode material can reduce pressure build-up within the battery that can be produced by zinc free of lead, mercury, or cadmium.
In one aspect a primary alkaline battery including a cathode, an anode, a separator, and an alkaline electrolyte. The cathode includes a hydrogen-absorbing cathode material. The anode includes zinc free of lead, mercury, or cadmium.
In another aspect, the invention features a method of manufacturing a primary alkaline battery. The method includes assembling a cathode, an anode, a separator, and an alkaline electrolyte to form the alkaline battery. The cathode includes a hydrogen-absorbing cathode material and the anode includes zinc free of lead, mercury, or cadmium.
In another aspect, the invention features a primary alkaline battery including a cathode including an active material that absorbs hydrogen more rapidly than an equivalent amount of electrochemically-produced manganese dioxide within an equivalent time interval, an anode including zinc free of lead, mercury, or cadmium, and an alkaline electrolyte.
The hydrogen-absorbing cathode material can include a nickel oxyhydroxide, a copper oxide, a chemically-produced manganese oxide, a silver oxide, a barium permanganate or a silver permanganate. The method also includes forming an anode including a zinc free of lead, mercury, or cadmium.
Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.